Power booster

ABSTRACT

An input piston carrying a double poppet valve which, during actuation, opens a high pressure fluid inlet in the input piston and seals a dump channel in an output poppet valve to form a hydraulic chamber during actuation. Upon deactuation the double poppet valve seals the high pressure fluid inlet channel in the input piston and opens the dump channel.

United States Patent Gladic Feb. 19, 1974 POWER BOOSTER I 2,870,607 11959 Voigt 92 129 2,779,314 1/1957 Vorech 91/372 [75] Inventor- Glad,Chlcago, 2,865,335 12/1958 Lewis 91 372 73 Assigneez InternationalHarvester Company, 3,040,713 6/1962 Stelzer 91/372 Chicago [IL 3,151,53010/1964 Brown 91/372 Filed! P 1972 Primary ExaminerPaul E. Maslousky[21] APP] 243,721 Attorney, Agent, or Firm-Floyd B Harman; John A.

Schaerli [52] U.S. Cl 91/372, 91/376, 92/168 [51] Int. Cl. FlSb 9/10,F16j 15/18 {\BSTRACT 58 Field at Search 91/370, 371, 372, 373, 434, PPlston Carrymg a double Poppet valve whlch 91/376; 92/168, 129, 167durmg actuation, opens a high pressure fluid inlet in the input pistonand seals a dump channel in an output [56] References Cited poppet valveto form a hydraulic chamber during ac- UNITED STATES PATENTS tuation.Upon deactuation the double poppet valve seals the high pressure fluidinlet channel in the input I 5:21:80!) 92/167 piston and opens the dumpchanneL 3:410:179 11/1968 Kytta et al. 92/167 1 Claim, 3 Drawing FiguresPOWER BOOSTER BACKGROUND OF THE INVENTION This invention relates tohydraulic booster valves for closed center systems and moreparticularly, to valves having a mechanically actuated double poppetmeans which controls the flow from the high pressure inlet as the flowto the dump outlet.

A hydraulic booster unit may be readily used wherever a source ofpressurized hydraulic fluid is available. Such units augment thephysical forces supplied by the operator to perform a function such asactuation of a braking system, etc. A disadvantage of using a hydraulicbooster, however, is that they are for the most part, very complicated,have many moving parts and are expensive.

SUMMARY OF THE INVENTION In accordance with the invention, a hydraulicbooster valve of a closed center type construction for boosting a manualinput is disclosed. The valve body has a first and second bore ofdifferent diameters, each bore carrying a piston slidably positionedtherein. A high pressure fluid inlet port opens into the first bore,passes through a channel in the first piston which extends from thefirst end thereof to the second end and then into the second piston andfrom there into an outlet port in the wall of the second bore. The firstpiston responds to external mechanical pressure exerted thereon whilethe second piston is subjected to the same mechanical action as well asthe force exerted by high pressure hydraulic fluid such that itovercomes the spring forces which tend to maintain it in a neutralposition. The channel through which the hydraulic fluid passes has afirst seating means located near its first end and a double poppet meansfloatingly carried therein such that the first poppet seats on saidfirst seat. The second end of the double poppet means extends out fromthe second end of the first piston such that it can seat in a seatingmeans provided in the channel of said second piston. Upon the exertionof mechanical pressure to the first piston, a hydraulic chamber isformed between the first and second pistons by the seating of the secondpoppet in the seating means provided in the second piston, such that themechanical force exerted thereon is multiplied and the components moveas the unit to deliver force to an outside force.

It is therefore an object of this invention to provide a hydraulicbooster assembly which is inexpensive and not unduly complicated.

Yet another object this invention is to provide a hydrauluc boosterassembly which produces position sense and force feel duringarticulation.

Still a further object of this invention is to provide a hydraulicbooster assembly which functions even upon the failure of hydraulicpressure driving means.

Another object of this invention is to provide a hydraulic boosterassembly having a functional indication denoting failure of thehydraulic driving means.

Still another object of this invention is to provide a single doublepoppet valve for a hydraulic booster assembly which controls the inletand outlet ports thereof.

Yet another object of this invention is to provide a hydraulic boosterassembly having very little dead time or lag.

These and other objects of this invention are achieved by linking asource of pressurized fluid to a hydraulic booster unit.

FIG. 1 is a sectional view showing the hydraulic booster assembly in areleased position;

FIG. 2 is a sectional view showing the hydraulic booster assembly in anactuated position; and

FIG. 3 is a perspective view of the double poppet valve.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 of thedrawing, numeral 10 designates a closed center type valve comprisinginput housing means 11, output housing means 12, and mounting bracketmeans 14 and 16.

Input housing means 1 1 includes an input bore means 18, an input piston20 positioned slidingly in said bore and having land means 22 andchannel means 24. When it is desired to actuate the input piston 20 tocause movement to the right, force is delivered through pedal means 104,to input shaft means 26, the end 28 thereof abutting ball means 30. Snapring means 34 and 36 retain said components in said abuttingrelationship. Further a tapered washer means 35 having a diameterslightly less than bore means 44 allows movement of shaft means end 28against ball 31). It is thus apparent that this movement is such thatthe shaft means 26 can be pivoted on ball means 30 withoutdisengagement, snap means 34 simply riding up on tapered washer means35, thus allowing delivery of force thereto at angles varying slightlyfrom 180. Additionally, a rubber boot means 38 shields the assembly fromexternal dirt, dust, moisture, etc.

The ball means 30 is positioned in channel means 44 and abuts firstshoulder means 40 of input piston means 20 thereby transferring forcesfrom shaft 26 thereto. The channel means 44 extends the entire length ofinput piston means 20 having a second shoulder means 46 as well as slotmeans 50. Reciprocatingly carried in channel means 44 is a double poppetvalve means 52 which regulates the flow of fluid passing from a pump(not shown) through inlet means 54 and land 22 and channel 24. As isapparent, when the tapered portion 56 of first poppet means 58 abutsshoulder means 46, the corresponding tapered portion 60 of second poppetmeans 62 extends out from the face 64 of input piston 20. Further, itshould be noted that, in a neutral position, a small gap 65 ismaintained between face 64 and front face 66 of output piston 68 becauseinput piston 20 is shorter than bore 18. As is apparent, the doublepoppet valve 52 thus is capable of regulating incoming fluid flowthrough input piston 20 and outgoing fluid flow through output pistonmeans 68.

The output housing 12 includes an output bore means 70 and an outputpiston 68 slidingly positioned in said bore. Said output piston 68having front face portion 66 and bored back portion 72. The outercircumference74 of said output piston being provided with a land means76 and seals 78 and 78a. The land means 76 connecting output inlet means80 and channel means 45 via passage means 82.

The bottom 84 of said bored back portion 72 is provided with a seatingmeans 86, said means accommodating the leading edge 88 of an outputshaft means 90. Output shaft 90 is provided with a bracket means 92which serves in conjunction with the closure means 94 to retain anoutput return spring means 96 therebetween. The output shaft 90 passesthrough or journals closure means 94 via aperture 98 and is furtherprovided with a rubber boot means 100 for insulation against dirt, dust,moisture. A snap ring means 102 secures closure means 94 in position. Asis apparent, a hydrostatic force output means may be substituted formechanical output means 90 without deviating from the invention hereindisclosed.

Assuming no clutch pedal force is acting on input piston 20, it will bepositioned to the left by the return spring means 96 which has actedthrough output piston 68 to overcome the resistance thereof. Themagnitude of the force of the return spring 96 in combination with thearea of effective surface 66 are selected such that an ample safetyfactor is provided to move the assembly to a neutral position oncepressure is removed from input shaft 26 via the pedal means 104. Itshould be understood that other return spring means can be provided, forexample, the clutch pedal itself may be fitted with a return springwhich urges it and input piston means 20 back into a neutral position, asecond suitable return means also being provided for outer piston means68.

In operation the hydraulic booster unit means is mechanically actuatedby the depression of pedal means 104 which is pivotally mounted on thesupport means 106. lnput shaft means 26 pivotally connects the pedalmeans 104 and extends centrally into the rearward end 108 of the inputcylinder 11. Pressurized fluid is introduced through port 54, as shownin FIG. 1, resulting in double poppet means 52 being carried to theright such that shoulder or bevel 56 of input poppet 58 seats againstshoulder 46 of input piston cutting off any flow thereof. It should beunderstood that if valve 10 were in a vertical position with inputhousing 11 being at the top, gravity would have caused the necessaryabutment, such that no fluid would have escaped, however, in thehorizontal position, some fluid may escape prior to closing the system.Regardless of which position valve 10 is in, however, input poppet 58will restrict fluid as soon as the system is pressurized or shortlythereafter. As is apparent, a very weak spring means such as springmeans 43 may be provided between face 55 and fact 58 such that doublepoppet 52 is always urged to the right in a closed position.

As is apparent upon actuation of pedal means 104, forces are transmittedto input piston 20 urging it to the right as shown in FIG. 2. Pistonmeans 20 moves into the space 65 carrying with it double poppet 52 untilshoulder means 60 of poppet means 62 seats in abutting relationship withshoulder means 67. Further, movement to the right of piston means 20results in the opening of the seal between shoulder means 46 and 56since the double poppet 52 is restrained against further movement by thenewly created seal between shoulders 60 and 67. As shown in FIG. 3, backsection 59 of poppet 58 is gapped or partially squared at 61 such thatan escape means is provided for fluid trapped therebehind.

Thus high pressure fluid is allowed to flow into slots 50 and gap 65 toexert force against the face 66 of output piston 68. Depending on howquickly an abutting relationship between shoulder means 60 and 67 isachieved, some fluid may escape to dump, however, this action simplyfloats double poppet means 52 forward into the desired abuttingrelationship. If for some reason output piston means 68 is located toofar to the right such that an abutting relationship can be immediatelycreated, double poppet 52 floats forward until shoulder means 46 and 56seat, avoiding excessive dumping of high pressure fluid. This situationis maintained until a combination of input shaft 26 and the forcesexerted by the high pressure fluid moves input piston means 20sufficiently to the right to achieve the desired seating between shouldmeans 60 and 67. This force acts to the right against the return spring96 creating an abutting seal between shoulders 60 and 67 and forming apower chamber. Since return spring 96 is relatively weak and thus exertsonly minimal opposition force.

When the output piston 68 has moved very slightly to the right, itsentire face 66 is available to carry the force exerted by the highpressure fluid wave, the advantage therefrom being apparent. After this,piston 20 and output piston 68 move as differential pistons, meaningthat the smaller input piston 20 attempts to move faster thereby keepingthe fluid outlet seated closed. If the input piston 20 is stopped, theoutput piston 68 stops when the clearance is such that both first poppetmeans 58 and a second poppet means 62 are seated, and there is no leak.If a piston leak exists or if poppet 62 unseats fluid would escape todump and output piston 68 would move back toward input piston 20, thusopening said first poppet means 58 admitting sufficient high pressurefluid to equilibrate the system.

A safety factor inherent in this assembly is that if for some reason thehigh pressure fluid system should fail, actuation would still bepossible by direct application of physical force through the pedal means104, and input piston 20 to the output piston 68. Further, thesubstantial increase in physical effort need would alert the operator tothe failure of the high pressure system, while still providing afunctioning assembly.

Upon release of the driving force on pedal means 104, the roles of thepistons are reversed and output piston 68 through return spring 96becomes the driving means urging input piston 20 to the left. As inputpiston moves leftwardly, an abutting seal, between shoulders 46 andfirst poppet means 58 which was created when the assembly stoppedrightward movement is maintained and the seal between shoulders 60 and67 is broken. Immediately upon breaking this latter seal, high pressurefluid is dumped via channel means 82 and land 76, and dump port 80,creating a low pressure system in front of poppet 58 and a high pressuresystem behind such that the abutting seal is maintained. Both inputpiston 20 and output piston 68 thus move leftward under the drivingforce of return spring means 96 which has been subjected to compressionuntil a released position is achieved.

Because the distance which the input piston must be moved to the rightduring actuation before the double poppet means 52 opens the fluid inputand closes the outlet is minimal dead time or lag is almost nil. Thatis, almost immediately upon depression of the pedal means, there is aresponse by the hydraulic booster unit means 10. If the motion startsfrom any arbitrary position of the system poppet valves are actuated byany small motion from rest and dead time is virtually zero.

An additional feature of this invention resides in the face that thetotal system employs only a very small volume of hydraulic fluid. Thus,extensive pressurization and pumping equipment is not required.

Although the invention has been described in connection with certainspecific embodiments, the principles are susceptible of numerous otherapplications 5 that will readily occur to those skilled in the art. Theinvention is, therefore, to be limited only as indicated by the scope ofthe appended claims.

Having thus described the various features of the invention, what Iclaim as new and desire to secure by Letters Patent is:

I claim: 1. A closed center hydraulic booster valve function ing with orwithout high pressure assist comprising:

housing means having chamber means therein and high pressure fluid inletand outlet means;

input piston and output piston means, each having passage means therein,operately secured in said chamber means whereby a power chamber isformed therebetween, said input piston passage means being connected tosaid high pressure fluid inlet, and having an inlet valve seat and adouble poppet valve means having a first and second end floatinglycarried therein, said input passage having means whereby movement ofsaid double poppet means is guided, said first end having a compressionspring means whereby it is biased to normally contact said inlet valveseat, said second end extending out from said input passage and havingan outlet valve means, said output piston passage means having an outletvalve seat for receiving said outlet valve means whereby when said inletvalve means is seated said outlet valve means is open and when saidinlet valve means is open said outlet valve means is closed;

a manual actuated input link means pivotally secured to said inputpiston means whereby actuating force can be delivered thereto atdifferent degrees of ana ball means carried between said manual actuatedinput link means and said compression spring, whereby said ball meanscenters said compression spring and facilitates pivotal movement of saidinput link means;

fluid energy source means interconnected with said fluid inlet means anda fluid return means interconnected with said outlet means;

an output link means pivotally secured to said housing means; and

a spring means continuously urging said input and ouput pistons into aneutral position.

1. A closed center hydraulic booster valve functioning with or withouthigh pressure assist comprising: housing means having chamber meanstherein and high pressure fluid inlet and outlet means; input piston andoutput piston means, each having passage means therein, operatelysecured in said chamber means whereby a power chamber is formedtherebetween, said input piston passage means being connected to saidhigh pressure fluid inlet, and having an inlet valve seat and a doublepoppet valve means having a first and second end floatingly carriedtherein, said input passage having means whereby movement of said doublepoppet means is guided, said first end having a compression spring meanswhereby it is biased to normally contact said inlet valve seat, saidsecond end extending out from said input passage and having an outletvalve means, said output piston passage means having an outlet valveseat for receiving said outlet valve means whereby when said inlet valvemeans is seated said outlet valve means iS open and when said inletvalve means is open said outlet valve means is closed; a manual actuatedinput link means pivotally secured to said input piston means wherebyactuating force can be delivered thereto at different degrees of angle;a ball means carried between said manual actuated input link means andsaid compression spring, whereby said ball means centers saidcompression spring and facilitates pivotal movement of said input linkmeans; fluid energy source means interconnected with said fluid inletmeans and a fluid return means interconnected with said outlet means; anoutput link means pivotally secured to said housing means; and a springmeans continuously urging said input and ouput pistons into a neutralposition.